X-ray transmission radiography is an important diagnostic tool for a wide variety of conditions. The need for improved resolution radiographs with minimal patient exposure has long been recognized for many areas of radiological imaging. X-ray film alone used as the recording media is capable of producing high quality radiographs. However, due to sensitivity limitations of the film to X-rays, it is necessary to use X-ray sensitive phosphor screens. The use of conventional film-screen necessitate a tradeoff between the thickness and spatial resolution due to lateral light spreading. Current x-ray film screens therefore limit the effectiveness of many radiographic procedures and necessitate unduly high patient exposure. The Phase I program demonstrated the feasibility of a new concept of producing X-ray convertor screens. During this program, novel convertor films of 5 cm x 5 cm were produced which had the high X-ray sensitivity, excellent light output and uniformity indicated that it will be possible to produce convertor screens with over 95% stopping power for 28 keV X-rays, light output at least 150% that of presently used convertors and limiting spatial resolution better than 20 Ip/mm. During phase II, we shall complete the development of the improved large- area film-cassette based on this new convertor screen and use it in film cassettes to measure large area phantoms. This work will involve methods of producing the large area X-ray converters required for standard mammographic format films. PROPOSED COMMERCIAL APPLICATION: Besides the enormous clinical X-ray imaging market, the proposed detector would find widespread use in instrumentation wherever high resolution X-ray detectors are used. X-ray imaging instruments currently have a very large commercial market. They may be applied to non-destructive testing systems, diffraction instruments, basic physics research, and other medical imaging systems.